Fix for bug that took ages to track down and was very subtle.

During authentication the flow of commands is as follows:
> SERVER aaaaaa
< SERVER bbbbbb
> BURST
< BURST
... what can happen is that between the two server commands we can introduce SERVER aaaa to server bbbbb again, from a different socket. As server aaaaa doesnt exist yet and we're waiting for it to say 
yes or no to our own SERVER command over at bbbbbb, it cant be found with FindServer.
Therefore we need a second list of servers that arent yet authenticated, but are waiting TO authenticate, by the pointer their socket has and the name they want to become after auth.
If two servers introduce themselves at the same time, triggering what was the race condition, both servers are disconnected with "ERROR :Negotiation collision" and must try again until only one succeeds.


git-svn-id: http://svn.inspircd.org/repository/trunk/inspircd@6802 e03df62e-2008-0410-955e-edbf42e46eb7

1 files changed, 17 insertions, 0 deletions

diff --git a/src/modules/m_spanningtree/treesocket2.cpp b/src/modules/m_spanningtree/treesocket2.cpp
index fa1e8ef15..c87e5d406 100644
--- a/src/modules/m_spanningtree/treesocket2.cpp
+++ b/src/modules/m_spanningtree/treesocket2.cpp
@@ -903,6 +903,20 @@ bool TreeSocket::Inbound_Server(std::deque<std::string> &params)
 	{
 		if ((x->Name == servername) && ((ComparePass(this->MakePass(x->RecvPass,this->GetOurChallenge()),password) || x->RecvPass == password && (this->GetTheirChallenge().empty()))))
 		{
+			/* First check for instances of the server that are waiting between the inbound and outbound SERVER command */
+			TreeSocket* CheckDupeSocket = Utils->FindBurstingServer(sname);
+			if (CheckDupeSocket)
+			{
+				/* If we find one, we abort the link to prevent a race condition */
+				this->WriteLine("ERROR :Negotiation collision");
+				this->Instance->SNO->WriteToSnoMask('l',"Server connection from \2"+sname+"\2 denied, already exists in a negotiating state.");
+				CheckDupeSocket->WriteLine("ERROR :Negotiation collision");
+				Instance->SE->DelFd(CheckDupeSocket);
+				CheckDupeSocket->Close();
+				delete CheckDupeSocket;
+				return false;
+			}
+			/* Now check for fully initialized instances of the server */
 			TreeServer* CheckDupe = Utils->FindServer(sname);
 			if (CheckDupe)
 			{
@@ -917,6 +931,8 @@ bool TreeSocket::Inbound_Server(std::deque<std::string> &params)
 				this->Instance->SNO->WriteToSnoMask('l',"Connection from \2"+sname+"\2["+(x->HiddenFromStats ? "<hidden>" : this->GetIP())+"] using transport \2"+name+"\2");
 			}
 
+			Utils->AddBurstingServer(sname,this);
+
 			this->InboundServerName = sname;
 			this->InboundDescription = description;
 			// this is good. Send our details: Our server name and description and hopcount of 0,
@@ -1050,6 +1066,7 @@ bool TreeSocket::ProcessLine(std::string &line)
 				this->LinkState = CONNECTED;
 				Link* lnk = Utils->FindLink(InboundServerName);
 				Node = new TreeServer(this->Utils,this->Instance, InboundServerName, InboundDescription, Utils->TreeRoot, this, lnk ? lnk->Hidden : false);
+				Utils->DelBurstingServer(this);
 				Utils->TreeRoot->AddChild(Node);
 				params.clear();
 				params.push_back(InboundServerName);